The invention relates to an apparatus for determining the identity and position of objects which are disposed in different fields of an area divided into a predetermined number of equal size fields, particularly for a determination of the identify and position of chess pieces on a chessboard.
DE-2,932,167 and GB-A-2,051,589 disclose, in connection with chess computers, the arrangement of the position of the chess pieces on the individual squares of a chessboard with the aid of permanent magnets attached to the underside of the chess pieces and with reed relays which are disposed on the underside of the chessboard and respond to the magnetic fields of the permanent magnets or similar contact switches which react to magnetic fields. If a chess piece is disposed on one of the squares of the chessboard, the magnetic field emanating from the permanent magnet of the chess piece causes the respective contact switch and thus, a circuit to be closed so that, in conjunction with a corresponding monitoring device, it can be determined on which squares of the chessboard chess pieces are disposed. In conjunction with a microprocessor and memory, the movement of the individual chess pieces can thus be reproduced and countermoves can be calculated by means of the processor and can be displayed, for example, by means of light-emitting diodes disposed in the individual squares of the chessboard or by means of liquid-crystal displays which indicate the row and column of the respective square of the chessboard.
However, the prior art devices are unable to indicate, in addition to the position of individual chess pieces, i.e. indicating whether a playing square is occupied or not, the identity of the chess piece that occupies the respective chess square. Thus it is necessary, for example, in solving chess problems by means of a chess computer, for the player to put the pieces onto the corresponding squares and simultaneously input by way of a keyboard which piece occupies the respective square. Only in the starting position of the chess pieces is it not necessary to provide additional input because this position input is stored in the program.
GB-A-2,103,943 relates to an electronic board game, particularly an electronic chessboard in which each playing piece of the electronic board game is provided with an identification device in the form of an electrical resonance circuit set to a certain resonant frequency so that it differs from the resonant frequency of the other playing pieces. Each square of the electronic chessboard is equipped with a scanning device in the form of a transmitter which emits a pulse to produce a resonant oscillation in the resonant circuit of a game piece located in the respective square. The resonant frequency picked up by a receiver is evaluated with the aid of a discriminator to determine the identity and position of the respective chess piece o the square in that the number of oscillations of the received signal are counted and the number of oscillations is compared with a stored value which is associated with the respective playing piece. Thereafter the evaluation device puts out a signal corresponding to the identity and position of the playing pieces on the square.
The above prior art device is based on a contactless identity and position determination and assumes accurate matching between the transmitter signal, the resonant circuit and the received signal. The required precise matching involves, considerable expenditures in the production and testing of the electronic game board and, makes it highly sensitive to extraneous interfering influences.
DE-A-3,309,817 also discloses a game employing a playing field composed of a plurality of individual fields and involving a plurality of playing elements in which the playing elements are provided with different codes which are detected by sensors in the fields. The outputs of the sensors are connected with a signal processing device through which the course of the game is stored and evaluated. In the prior art game, the coding of the playing elements is composed of rod-shaped permanent magnets of given lengths while the sensors in the individual playing fields are Hall sensors which are connected over a common current path with a constant current source. As a consequence of the different lengths of the individual rod magnets and possibly different polarities the Hall sensors are able to detect the position as well as the identity of the respective playing element.
In this prior art device it is necessary to accurately position the individual playing elements so that the Hall sensors are influenced in a suitable manner by the rod magnets of the playing elements. For this purpose, a recess is provided into which the respective playing elements must be inserted to unequivocally position them.
In addition, magnetic shields are required so that adjacent playing elements are not influenced. Here again it is necessary to very accurately align the Hall sensors and the rod magnets and, as a result of the limited length of the individual playing elements, only a limited number of different playing elements can be identified by rod magnets of different lengths.